Ms Rice was quickly given a taste of life in the war torn Iraqi capital, as her C-130 military transport plane was forced to circle for 45 minutes over an airport temporarily closed by insurgent rocket attacks, her spokesman said.
Her visit to Iraq comes as six more US soldiers were killed in Iraq, bringing to 16 the number of American personnel killed this week.
The US envoy met with Iraq's Prime Minister Nuri al-Maliki, who is desperately trying to hold together a national unity coalition.
"I do think he has the strength. I think he's a very good and strong prime minister," Ms Rice told reporters on her plane.
She also praised Mr Maliki's steps to purge his security forces of rogue elements supporting sectarian death squads.
"The government and Prime Minister Maliki believe very strongly that their most important work now is to be done in getting the political bargain in place in terms of national reconciliation," she added.
Ms Rice's visit came after Iraq's political leaders signed a solemn pledge on Monday to end the sectarian bloodshed.
It’s the latest attempt by Mr Maliki's embattled government to halt the vicious sectarian war engulfing the country.
Surge in attacks
But concerns have already been expressed about how willing the Iraqi parties are to implement their promises.
Violence continues in the strife-torn country killing more than 100 Iraqis every day amid a surge in bomb attacks and death squad murders.
"Our role is to support all the parties and indeed to press all the parties to work towards that resolution promptly," Ms Rice said.
"Obviously the security situation is not one that can be tolerated and it isn't one that has been helped by political inaction," she warned.
She met briefly with Mr Maliki at his offices in the heavily fortified Green Zone before going to the US embassy.
There she met other Iraqi leaders from both sides of the sectarian divide.
Casualties mounting
Ms Rice's last visit to Iraq was on April 26, when she came with Defence Secretary Donald Rumsfeld to congratulate Mr Maliki on being chosen to form a coalition government.
Since then, US troop numbers in Iraq have climbed from 132,000 to 142,000.
Suicide bomb attacks are now running at all time high, bomb attacks in general at a yearly high and civilian casualties pushing 3,000 per month.
US casualties are also mounting. Four more soldiers were killed on Wednesday in Baghdad when their unit was attacked by gunfire and mortars, while two marines died in action in the mainly Sunni western province of Anbar.
Since Monday, 16 US soldiers have been killed, mostly in Baghdad, in a spike in casualties that brought the number killed since March 2003 to 2,732, according to an AFP count based on Pentagon figures.